Marvel Studios' Guardians of the Galaxy Vol. 2 follows the unlikely band of heroes' latest adventures as they explore the outer reaches of the cosmos. In the sequel, the group must learn how to stand united while trying unravel the mystery of Star-Lord/Peter Quill's heritage.

Writer and director James Gunn's blockbuster movie boasts an all-star cast that includes Dave Bautista as Drax the Destroyer, Elizabeth Debicki as Ayesha, Tommy Flanagan as Tullk, Karen Gillan as Nebula, Sean Gunn as Kraglin, Laura Haddock as Meredith Quill, Pom Klementieff as Mantis, Chris Pratt as Peter Quill/Star-Lord, Michael Rooker as Yondu, Kurt Russell as Ego, Zoe Saldana as Gamora, Sylvester Stallone as Stakar Ogord and Chris Sullivan as Taserface. Bradley Cooper and Vin Diesel return to voice Rocket Raccoon and Baby Groot, respectively. David Hasselhoff makes a cameo appearance as himself, while Seth Green also returns to voice Howard the Duck (who first appeared in a Guardians of the Galaxy post-credits scene in 2014).

Look out for for other surprise cameos (including Miley Cyrus as the voice of Mainframe).

"As the Marvel Cinematic Universe continues to expand, it becomes clearer that there are two kinds of films in the series: those that introduce or embellish characters and include events that have ongoing consequences within this on-screen world, and those that merely act as a bridge from one big story point to another, allowing audiences to spend time with beloved characters and to watch some mammoth, special-effects-heavy fight sequences that ultimately don't add up to much," Duralde writes. "The first Guardians of the Galaxy falls firmly into the former category, while Guardians of the Galaxy Vol. 2 fits into the latter." It's unlikely that the sequel will generate new fans, "but if you like the flavor of these movies, you'll enjoy this second bite."

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"Most of these maverick mercenaries prove rather less charming the second time around; they're like bickering family now and not in an amusing way," McCarthy writes. "Burrowed in somewhere among the more or less random space battles, showdowns, shoot-outs, personal fights and hair-breadth encounters with instant oblivion…is the opportunity for Peter Quill to get to know his father." Pratt and Russell's scenes together "are the best in the film," he adds. "The heavy, elaborate action is both plentiful and rote; in their geometric design and execution, the special effects feel exceedingly computer-generated. Unlike, say, the best space battles in the Star Wars series, the frantic ballistic parrying here often makes the viewer feel as if trapped inside a pinball machine...Guardians of the Galaxy Vol. 2 plays like a second ride on a roller coaster that was a real kick the first time around but feels very been-there/done-that now."

"Guardians of the Galaxy Vol. 2 can't match the sneak-attack surprise of its predecessor. You can only do that once. The good news, however, is that the follow-up, while taking on some CGI bloat and sequel slickness, hasn't lost its love for inspired lunacy. Hanging with Quill and his mercenary space misfits is still everything you'd want in a wild summer ride," Travers writes, noting that Gunn "never runs out of fresh funny business" for the Guardians. "Remarkably, Guardians of the Galaxy, Vol. 2 still has the loosey-goosey feel of a rogue epic that the kids made when the grown-ups weren't watching," he writes. "Only a turd blossom could resist it."

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"Nothing dooms a comic book movie quicker than when it takes itself too seriously...Maybe that's why Guardians of the Galaxy was such a welcome and delirious blast of laughing gas when it hit theaters nearly three years ago," Nashawaty writes. "Alas, in Guardians of the Galaxy Vol. 2, the gag is starting to feel like it's getting a bit old. It's still a good Marvel movie (at times, a very good one), but it's a come down from the dizzying highs of the first installment. The laughs are still there, but they're less involuntary…Worse, the gang which had so much chemistry together is split up and separated for most of the film to tackle their own storylines."

"Just like the first one, Guardians of the Galaxy Vol. 2 is a winning and wonderfully relatable gem of crazy...It's missing some of the ragtag underdog charm of 2014's instaclassic Guardians that made it one of the best Marvel efforts ever," Truitt writes. "Yet Vol. 2 becomes in its own way a more confident and well-rounded movie by experimenting with character relationships, familial rivalry and its own successful template." One of the franchise's best qualities is that it's "the least beholden to the bigger Marvel Cinematic Universe." The action and story are "epic," as fans are expecting, "but the small quirks—like its mini sentient tree—make a big difference."

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"The ruling aesthetic of the Marvel universe is now bloat," Edelstein writes. There are action scenes aplenty, "but there's no suspense. It's all just fodder." In this round, "the ratio of laughs to one-liners is lower than in the first Guardians." While it's "not all disposable," Edelstein argues that it has a "corporate" vibe—"and of the most depressing kind: It's not enough that you've paid for this product. You have to sit through commercials for the next one and the next and the next. (There are four—count 'em—teasers during the credits.) The problem isn't that I think this is empty-calorie junk food," he writes. "It's that, on the evidence, Marvel does, too."

"Guardians of the Galaxy Vol. 2 probably couldn't, and definitely doesn't, recapture the sweet and singular silliness of the original, though the new edition...has its rewards," Morgenstern writes. "The opening credits are delightful, with Baby Groot—a twiggily downsized version of the sentient tree voiced by Vin Diesel—dancing blissfully to the strains of Electric Light Orchestra's 'Mr. Blue Sky' while, behind him, desperate Guardians fight for their lives against enormous tentacled monsters. Subsequent combat sequences paint extravagant action in pastel hues. Cartoonish characters reveal touching inner lives. Still, the galaxy isn't big enough to contain the meandering plot, which sends the hero, Chris Pratt's Peter Quill, on a quest to discover his identity…That's the corporate calculus at work—turning a lighthearted goofball into a seeker of weighty truths, and, in the process, making him a spectator to much of the action."

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"In the context of modern garden-variety escapist cinema, there's nothing inherently wrong with Guardians of the Galaxy Vol. 2…But this gag- and plot-stuffed follow-up is also emblematic of all we've come to settle for in movie entertainment: It feels not so much crafted as squirted from a tube. In striving to surprise us every minute with its seen-it-all irony, Guardians Vol. 2 is actually the surprise-spoiler of all time—our every 'Wow!' or 'Haha!' has been scripted in advance," Zacharek writes, arguing there are enough plots in the film "to fill a dozen galaxies."

"Shot for shot, line for line, it's an extravagant and witty follow-up, made with the same friendly virtuosic dazzle. Yet this time you can sense just how hard the series' wizard of a director...is working to entertain you. Maybe a little too hard," Gleiberman writes. "Guardians of the Galaxy Vol. 2 is an adventure worth taking, and the number of moviegoers around the planet who will want to take it should prove awe-inspiring. But it doesn't so much deepen the first Guardians as offer a more strenuous dose of fun to achieve a lesser high." Bautista and Cooper have some of the best jokes, but it's Pratt who "keeps his badass-lite swagger irreverent and commanding."

Guardians of the Galaxy Vol. 2 is rated PG-13. It's available in standard, 3D and IMAX 3D formats.